Leptin Turns Fat Cells Into Fat-Burning Cells

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Experimental Leptin Therapy May Eventually Aid in Weight Loss

Feb. 9, 2004 -- Increasing levels of a hormone that regulates
body weight may help convert fat-storing cells into fat-burning ones, according
to a new animal study.

Researchers say if the same principle holds true in humans, the
findings may offer a "quick and safe solution" to obesity and aid in
weight loss efforts.

The study, published in the Feb. 17 issue of the Proceedings
of the National Academy of Sciences, found that increasing the levels of
the hormone known as leptin in rats led to significant weight loss in the
animals.

Researchers say leptin therapy caused weight loss by triggering
a change in the structure and function of the rat's fat cells, from fat-storing
to fat-burning. This occurred by increasing the action of mitochondria within
the cells. Mitochondria are the main source of energy in cells.

Leptin Changes Fat Cells

"This is the first careful examination of the fat cells
after leptin therapy," says researcher Roger Unger, MD, director of the
Touchstone Center for Diabetes Research at the University of Texas Southwestern
Medical Center at Dallas, in a news release.

"The structure of the cells changes from the normal
appearance of a fat cell to a very novel cell that's really never been seen
before," says Unger. "The ability to convert fat cells into fat-burning
cells may suggest novel therapeutic strategies for obesity."

In the study, researchers looked at the effects of injecting
rats with the leptin gene. Two to four days after receiving the injection,
researchers found leptin levels rose to 50 times higher than those found
normally in rats and then tapered off.

Compared with normal rats fed a restricted diet, the study
showed that animals that got the leptin injection experienced much greater
weight loss and lost an average of about 26% of their total body weight 14 days
after leptin therapy began.

Researchers say the rats receiving leptin therapy were healthy
and active but had a decreased appetite. But the normal rats fed a restricted
diet were constantly searching for food and had lower levels of physical
activity.

When the researchers examined the rats' cells under the
microscope, they found that rather than storing fat, the cells were full of
fat-burning mitochondria.

Researchers say the next step is to learn how to break down the
body's natural defense system against leptin produced in the fat cells of
humans, which is designed to prevent a wasteful loss of the body's fat
stores.

"Such an effect would make obesity impossible and might
lead to a quick and safe solution to the obesity problem," write the
researchers.